Power loss

[Keith gigabyte]

Brand new to this forum. Me..2001 crew cab 8 foot bed Chevrolet lb7 duramax
Owned for 3 years bought with 140k miles now has 172
Replaced water pump at about 150k.
Issue now while towing 8-9k lb camper won't go over 55 on a hill check engine light on while pulling hill goes out shortly after leveling out. Can set cruise on 70 mph on level. Rpms about 2500 loud fan noise is about best I can describe it..like the radiator fan blowing very hard when power loss.
Have not been able to pull codes yet. Oil and fuel filter change about 500 miles ago. Did not help or change problem. Problem seems to be getting worse
Any help is appreciated
Gigabyte

 

[830king]

Gonna need the codes to help. But for now let's start with the basics.... how fresh is the fuel/air filters? Do you have a way to monitor actual vs. desired rail pressure?

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[IOWA LLY]

Need to get us the codes.

I'm gonna take a wild ass guess and say it's low on rail pressure from worn out injectors, or a worn out cp3 pump since you just replaced the fuel filter.

But without codes it's just that. A guess....

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[Tothemax]

Need to get us the codes.

I'm gonna take a wild ass guess and say it's low on rail pressure from worn out injectors, or a worn out cp3 pump since you just replaced the fuel filter.

But without codes it's just that. A guess....

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Got my vote on this ^^^

 

[Bfox111]

Need codes. But my guess is your fuel filter head needs rebuilt since it is an 01 and more than likely has not been done. It is fairly cheap and easy to do.